Bose speaker mosfets

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Bear
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Bose speaker mosfets

Post by Bear » Tue Feb 23, 2010 1:23 pm

Hi everybody! I am trying to repair the left rear speaker amplifier for a 1966 Infinity I30 for a good friend of mine. There are 4 mosfets on the board with the markings of "A415" "137110" on them.
They are made by STMicroelectronics. Bose will sell me a new(rebuilt?) amp for around $100.00.
Bose will give me no information on the xistors nor sell me replacement xistors. STMicroelectronics says that the 137110 designation indicates that they are proprietary parts and they have a non-
disclosure agreement w/Bose. They are in a TO220FP pkg. I have seen where some people have suggested replacement xistors of TIP41 & IRFZ44. Both of these items are in a TO220AB pkg. I am skeptical of using these replacement parts as I have seen no information as to the reliability of these parts(5 miles or 5 minutes?). Thought I would check here and see if anyone has any experience with replacing the original STMicro parts. Obviously I do not care if the replacement parts are made by STMicro just as long as they will be reliable. The voicecoil on the speaker is about 1 or 2 ohms.

Thanks in advance

Dennis

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Externet
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Re: Bose amplifier mosfets

Post by Externet » Tue Feb 23, 2010 4:25 pm

Get the suspected equivalent mosfets, replace them and everything else blown in the circuit. If you do not get the expected fit, quality sound, or distortion, or noise, power, or whatever, buy the amplifier from Bose and keep the bad one as spares bank.
The reliability of 5 seconds to release smoke or 50 years mostly depends on the health of the rest of components and the happycranking of the volume knob. The maximum volume achievable is NOT at the maximum clockwise knob. :smile:

(There were no Infinitys in 1966)
Miguel
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Bob Scott
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Re: Bose speaker mosfets

Post by Bob Scott » Tue Feb 23, 2010 5:37 pm

Bear wrote:STMicroelectronics says that the 137110 designation indicates that they are proprietary parts and they have a non-disclosure agreement w/Bose. They are in a TO220FP pkg. I have seen where some people have suggested replacement xistors of TIP41 & IRFZ44. Both of these items are in a TO220AB pkg. I am skeptical of using these replacement parts as I have seen no information as to the reliability of these parts(5 miles or 5 minutes?).
The TIP41C is an excellent universal NPN power transistor. Cheaper and better than most other TO-220 NPN power transistors. It is well know for its reliability and robustness and an excellent replacement choice..... but it is not a FET. Who recommended this bipolar transistor as a replacement for a FET? It will not replace a FET. Datasheet at http://www.fairchildsemi.com .

The IRFZ44 is probably the most commonly used N channel power MOSFET, and one of the most powerful for its size. They make so many of these that the price of them is way low, like 79 cents each. If you were looking for a MOSFET with inferior specs, you would choose this one instead because it is cheaper and better, like the TIP41C but this one is a MOSFET and way more powerful. Datasheet at http://www.irf.com .

Do you have a schematic of the BOSE amplifier that you could post here? We can't recommend substitute part numbers unless we know if they are P or N channel, or what voltage and power levels are etc.
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Re: Bose speaker mosfets

Post by Bear » Fri Mar 05, 2010 3:52 pm

Hi again Externet & Bob Scott!! Thank you for your responses! I got the info re the TIP41 off the net, from a company that supposedly repaired Bose equipment. He said that "there is no "good" replacement for the Bose xistor/mosfet and that he had a lot of units come in with the TIP41 soldered in. He never really stated whether the original item was a xistor or mosfet. Another site I looked at said that the replacement was a mosfet made by IR the p/n was IRFZ44N. I did not trust either one of these sites. I was not filled with great confidence in the quality of their information as the TIP41 and the IRFZ44N are in a TO220AB package and not the TO220FP package like the Bose.

I came across another site that said that the exact replacement was an IR p/n IRFZI24N. His backup information was excellent and the IRFZI24n is in a TO220FP package. He had pictures of the board and other qualifying information that was spot on. I am going to order the IRFZI24N from Digikey and install them along with some capacitors that he recommended.

I am sorry that it took so long to reply to you, but things got a little hectic here at home.
Again thank you.

P.S. Externet...you are correct it is a 1996 Infinity. (brain fart on my part)
Take care all

Dennis

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Re: Bose speaker mosfets

Post by haklesup » Fri Mar 05, 2010 6:05 pm

(There were no Infinitys in 1966)
No MOSFETS either :razz:

If the IRFZI24N don't work well then your best chance to match them is to curve trace one (if any of them work) and try to specify the replacement by parameter search. Although a host of FETs may work, you may need a good match to the others or its complement for the best sound.

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Bob Scott
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Re: Bose speaker mosfets

Post by Bob Scott » Sat Mar 06, 2010 8:13 am

Hey Bear. This is a bit confusing. Normally if I found the number A415 on a power transistor, I would assume that it is a normal part number for a PNP silicon bipolar transistor, not a FET. With the 2SA/B/C/D Japanese numbering system, the FETS usually start with 2SK, 2SJ, or just K or J.
If some of these amps blow the original and the TIP replacement, I would look into a couple of things:

The TIP41/a/b/c is a NPN transistor available in different voltages. The blank/a/b/c indicates 40/60/80/100V. I wold recommend the "C" type. uBut original part number indicates and PNP is required. Try a TIP42C. It is PNP.

Do you have a schematic you could post? Can you sketch one?

Bob
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Re: Bose speaker mosfets

Post by CeaSaR » Sat Mar 06, 2010 8:27 am

Bob Scott wrote:(snip)Normally if I found the number A415 on a power transistor, I would assume that it is a normal part number for a PNP silicon bipolar transistor, not a FET. With the 2SA/B/C/D Japanese numbering system, the FETS usually start with 2SK, 2SJ, or just K or J.(snip)
Bob,

Other than the A in the "JNS", are there any additional considerations that would lead you to this conclusion with
the other info given? I'm just curious because I don't have the years of experience with parts that others do.

CeaSaR
Hey, what do I know?

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Bob Scott
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Re: Bose speaker mosfets

Post by Bob Scott » Sat Mar 06, 2010 9:07 am

CeaSaR wrote:Other than the A in the "JNS", are there any additional considerations that would lead you to this conclusion with the other info given? I'm just curious because I don't have the years of experience with parts that others do.

CeaSaR
Hi Ceasar. What is "JNS"?
I haven't reached any conclusion. There is not enough information. But the parts that Bear was recommended by a "tech" (TIP41, IRFZ44) are incompatible with each other just from a polarity point of view. Also, you can't sub a bipolar transistor with a power MOSFET and vice versa. It won't work.

If the transistors are indeed house numbered, then all of the markings on the transistors are gibberish.

A diagram could clear it up....or someone with Bose technical experience. If this mystery amp is anything like most other brands, there is probably other damage involved besides output failure. There is a good likelyhood of driver damage and possibly bias circuit (diodes, thermistor) damage.

Bear: Does this circuit have emitter resistors on the output transistors? FETs don't seem to need them according to my schematic of a Hafler D200.
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CeaSaR
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Re: Bose speaker mosfets

Post by CeaSaR » Sat Mar 06, 2010 2:54 pm

Bob Scott wrote:..."JNS"?
Japanese Numbering System, JNS for short. Sorry for the confusion.

CeaSaR
Hey, what do I know?

Bear
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Re: Bose speaker mosfets

Post by Bear » Thu Mar 11, 2010 8:52 am

Hi everybody! Here is the website that I got my info re the mosfets. http://www.zr1netregistry.com/Bose2.pdf. I hope this link works. The board pictured in the
article looks almost exactly like the one I have. I am going to run with his information and order the parts he suggests to replace. Of course I could always send it back to Bose to be repaired, but as has been said before "what fun is that".

Take care all

Dennis

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Re: Bose speaker mosfets

Post by hypersparc » Mon Feb 22, 2021 10:22 pm

Hello,

You can't randomly pick a transistor because it looks like may fit based on the package. I have a Bose amplifier that's more than 25 years old.
To replace the ST-Micro 137110 you will need to first determine what type of transistor is it. MOSFET, NPN, IBGT and then determine it's specs.
The best tool for this is a curve tracer. SInce, I don't really nave one or need one I need to create the same effect. Curve tracers were produced
years ago by Tektronix's and other. Today they have SMU (source measuring units). There are DC specs and AC specs. Curve tracers don't test
the AC specs . With a simple setup with two power supplies can a few resistors you can easily find the DC specs. You can determine it if BJR, JFET,
MOSFET, etc. Bi-Polar devices are current amplifiers while FET's are Voltage to current (transconductance Amps). The most important paramenter
in BJT is it's gain current gain and MOSFET is it's threshold or Vth. SInce, the Bose Amp I have is a Class D or switching design there is almost 100 percent chance this is MOSFET or IGBT type transistor. These types of Amps are completely non-linear. They rely on switching current into a capacitor to produce a voltage and then having the inductor filter out high frequency noise. These Amps are efficient because the transistors are either fully on or fully off. The only power loss during the switching time. So if want to find a suitable replacement. Find a transistor with the same Vth or threshold for turn on and fastest switching time with the least amount of input capacitance that can handle the most current and and suitable V drain to source voltage. The good news is that power transistors process technology much better than 25 years ago. You can probably find transistors in the same form factor than can handle 600 Volts and 60 Amps. You probably on need maybe 25 Volts and 15 Amps to replace 127110. There may be other devices such a reverse diode to protect negative currents but this can be detected when you do a DC test for parameters. I'll try to report the parameters that I measure and a suitable replacement based on the specs.

I saw a post with two transistors recommended. One a Nominal threshold of 4 volts and the other 1 volt. Completely incompatible. I've seen nothing on the web that actually has measured the ST 137110 device.

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